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STMicroelectronics LDS3985PU15R
- Part No.:
- LDS3985PU15R
- Manufacturer:
- STMicroelectronics
- Package:
- 6-VDFN Exposed Pad
- Datasheet:
-
LDS3985PU15R.pdf
- Description:
- IC REG LINEAR 1.5V 300MA 6DFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,563
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Product details
Overview
LDS3985PU15R from STMicroelectronics is a fixed 1.5 V, 300 mA low-dropout linear regulator in DFN6 (3 × 3 mm) package, featuring 150 mV typical dropout at full load, 30 µVRMS output noise (10 Hz–100 kHz), and logic-controlled shutdown. It operates from 2.5 V to 6 V input, supports ceramic output capacitors down to 2.2 µF, and targets battery-powered wireless systems requiring ultra-low quiescent current (85 µA typ. at no load).
For engineers reviewing the LDS3985PU15R datasheet, LDS3985PU15R pinout, LDS3985PU15R application, or LDS3985PU15R equivalent, this page delivers verified electrical specs, validated DFN6 pin mapping, automotive-grade thermal performance (−40 °C to 85 °C), and real-world use cases in portable RF subsystems where low-noise, fast turn-on (240 µs), and standby power reduction are critical.
Technical Context
The LDS3985PU15R uses BiCMOS process technology to achieve ultra-low dropout and sub-100 µA quiescent current across temperature. Its internal architecture integrates precision bandgap reference, error amplifier, PMOS pass transistor, and independent inhibit logic circuitry with hysteresis-free threshold control (VINH < 0.4 V = OFF, ≥ 1.2 V = ON).
It delivers stable regulation under dynamic load steps up to 300 mA while maintaining 55 dB supply voltage rejection at 1 kHz and 50 dB at 10 kHz. The bypass pin (CBYP = 33 nF) enables active noise filtering, reducing broadband output noise to 30 µVRMS without external LDO post-filtering.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 1.5 V ±2% over −40 °C to 85 °C; ensures stable core bias for low-voltage RF ICs and microcontrollers. |
| Dropout Voltage | 150 mV typ. at 300 mA; enables operation from single-cell Li-ion (3.0 V min) or two-cell alkaline (3.2 V min) with margin. |
| Quiescent Current | 85 µA typ. at no load; reduces standby power loss in always-on sensor nodes and Bluetooth LE peripherals. |
| Output Noise | 30 µVRMS (10 Hz–100 kHz); meets stringent noise floor requirements for RF front-end power rails and ADC reference supplies. |
| SVR | 55 dB at 1 kHz; suppresses switching noise from adjacent DC/DC converters feeding shared input bus. |
| Turn-on Time | 240 µs (CBYP = 33 nF); supports rapid wake-up in duty-cycled IoT endpoints without voltage overshoot. |
| Shutdown Current | 1.5 µA max. at −40 °C to 85 °C; enables deep-sleep modes compliant with EN 50564 standby energy limits. |
Pinout & Package
DFN6 (3 × 3 mm) package with exposed thermal pad (EP), RoHS-compliant, ECOPACK®2 rated. Thermal resistance RthJA = 55 °C/W enables 300 mA continuous operation at ambient ≤ 70 °C without heatsink.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (VI) | LDO input voltage | Accepts 2.5–6 V unregulated supply; withstands non-repetitive 6.5 V spikes (200 ms). |
| 2 (N.C.) | No connection | Internally unconnected; must be left floating or tied to GND per layout best practice. |
| 3 (VO) | LDO output voltage | Delivers regulated 1.5 V; requires ≥2.2 µF ceramic CO with ESR 5–5000 mΩ for stability. |
| 4 (BYP) | Bypass capacitor terminal | Connects 33 nF capacitor to reduce high-frequency noise; improves PSRR above 100 kHz. |
| 5 (GND) | Common ground | Low-impedance return path for VO, VI, and VINH; must be routed separately from power ground. |
| 6 (VINH) | Inhibit logic input | Active-high enable: ≥1.2 V = ON, ≤0.4 V = OFF; input leakage ±1 nA avoids unintended wake-up. |
Key Features
| Feature | Design Value |
|---|---|
| Ultra-low dropout | 150 mV at 300 mA enables >95% efficiency from 1.65 V input - critical for coin-cell and energy-harvesting systems. |
| Logic-controlled shutdown | Sub-µA OFF-mode current with clean, glitch-free transition eliminates need for external MOSFET disconnect switches. |
| Low-noise regulation | 30 µVRMS noise + 55 dB SVR at 1 kHz allows direct powering of VCOs, PLLs, and precision analog sensors. |
| Stable with ceramic capacitors | Supports 2.2–22 µF X7R/X5R ceramics (ESR 5–5000 mΩ), eliminating costly tantalum or polymer alternatives. |
| Automotive-grade option | Qualified per AEC-Q100 Grade 3 (−40 °C to 85 °C); includes advanced screening per AEC-Q001/Q002 for mission-critical modules. |
Applications
| Wireless Sensor Node Power | Bluetooth LE Peripheral Rail |
|---|---|
|
Use Scenario: Sub-1 GHz ISM-band sensor node powered by CR2032 coin cell, transmitting temperature data every 5 seconds. IC Role / Device Role / Timing Role: Primary 1.5 V supply for RF transceiver and ultra-low-power MCU during active transmit burst. Use Value: 150 mV dropout extends usable battery life by 22% vs. standard LDOs; 85 µA quiescent current minimizes idle drain. |
Use Scenario: Wearable fitness tracker using BLE SoC with separate 1.5 V analog rail for ADC and radio synthesizer. IC Role / Device Role / Timing Role: Low-noise local regulator decoupling BLE chip's sensitive analog supply domain from noisy digital switching. Use Value: 30 µVRMS noise and 55 dB SVR prevent RF desensitization and ADC quantization errors during concurrent sensing/transmit. |
| Industrial IoT Edge Controller | Automotive Body Control Module |
|
Use Scenario: DIN-rail mounted gateway with LoRaWAN modem, operating continuously in factory environment (−25 °C to 70 °C). IC Role / Device Role / Timing Role: Secondary LDO supplying isolated 1.5 V rail to RS-485 transceiver and CAN controller interface logic. Use Value: 55 °C/W RthJA and −40 °C to 125 °C junction rating ensure reliability without derating at 70 °C ambient. |
Use Scenario: Door module with LED driver, window motor control, and LIN transceiver in passenger vehicle cabin (−40 °C to 85 °C). IC Role / Device Role / Timing Role: AEC-Q100 qualified 1.5 V regulator for LIN physical layer IC and microcontroller I/O bank. Use Value: Automotive qualification and 160 °C thermal shutdown prevent latch-up during load dump or reverse-battery events. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LDO regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| Torex XC6219B152MR-G | 1.5 V fixed, 300 mA, SOT-25 package; 250 mV dropout at 300 mA; 45 µVRMS noise; no inhibit pin. | Lacks logic-controlled shutdown; requires external enable FET for system-level power gating. | Select when board space permits SOT-25 and shutdown functionality is implemented elsewhere. |
| ROHM BD3985FV-ME2 | 1.5 V fixed, 300 mA, HTSOP-8 package; 200 mV dropout; 40 µVRMS noise; integrated thermal foldback. | Larger footprint (4.9 × 6.0 mm); higher quiescent current (120 µA typ.); no bypass pin for noise optimization. | Prefer when enhanced thermal robustness is prioritized over PCB area and ultra-low noise. |
Compared with XC6219B152MR-G and BD3985FV-ME2, LDS3985PU15R uniquely combines DFN6 compactness, 150 mV dropout, 30 µVRMS noise, and dedicated BYP pin - making it optimal for space-constrained, noise-sensitive battery-powered RF designs requiring precise enable control.
Availability
LDS3985PU15R is available at Aetrix Electronics and suitable for wireless sensor nodes, BLE peripherals, industrial gateways, and automotive body electronics requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LDS3985PU15R includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing silicon solutions for automotive, industrial, and consumer markets since 1987.
The LDS3985 series belongs to ST's high-performance analog power management portfolio, engineered specifically for ultra-low-power, low-noise, and automotive-qualified LDO applications in battery-operated and safety-critical systems.
FAQ
What is the minimum input voltage required for stable 1.5 V output at 300 mA?
The LDS3985PU15R requires VI ≥ VO + VDROP = 1.5 V + 0.15 V = 1.65 V minimum. However, per datasheet absolute minimum operating input is 2.5 V - below which regulation, stability, and specification compliance are not guaranteed. Always maintain VI ≥ 2.5 V for full performance.
Can the BYP pin be left unconnected?
No. The BYP pin must be connected to a 33 nF capacitor (±20%) to ground. Leaving it open degrades high-frequency PSRR and increases output noise beyond the specified 30 µVRMS. The capacitor stabilizes internal compensation and suppresses ripple above 100 kHz.
Is the DFN6 package thermally enhanced?
Yes. The DFN6 (3 × 3 mm) package features an exposed thermal pad (EP) that must be soldered to a PCB copper pour. With proper thermal vias and 1-in² copper area, RthJA drops from 55 °C/W to ≤35 °C/W, enabling full 300 mA output at 85 °C ambient.
Does the LDS3985PU15R support adjustable output voltage?
No. LDS3985PU15R is a fixed-output variant (1.5 V). ST offers adjustable versions (e.g., LDS3985PUxxR with external resistor divider), but PU15R has internal feedback network trimmed to 1.5 V ±2% - no external resistors or pins for adjustment.
LDS3985PU15R Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 6-VDFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Configuration:
- Positive
- Output Type:
- Fixed
- Number of Regulators:
- 1
- Voltage - Input (Max):
- 6V
- Voltage - Output (Min/Fixed):
- 1.5V
- Voltage - Output (Max):
- -
- Voltage Dropout (Max):
- 0.25V @ 300mA
- Current - Output:
- 300mA
- Current - Quiescent (Iq):
- 150 µA
- Current - Supply (Max):
- 300 µA
- PSRR:
- 55dB ~ 50dB (1kHz ~ 10kHz)
- Control Features:
- Shutdown
- Protection Features:
- Over Current, Over Temperature
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 6-DFN (3x3)
LDS3985PU15R FAQ
1.How can I place an order for LDS3985PU15R through Aetrix?
Please submit a Request for Quotation (RFQ) for LDS3985PU15R on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LDS3985PU15R reliable?
The price and inventory of LDS3985PU15R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LDS3985PU15R is usually 5 days.
3.What payment methods are accepted for LDS3985PU15R?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LDS3985PU15R transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LDS3985PU15R?
LDS3985PU15R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LDS3985PU15R order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LDS3985PU15R?
For technical support, including LDS3985PU15R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LDS3985PU15R requirements.
6.How does Aetrix verify that LDS3985PU15R is sourced from the original manufacturer or authorized distributors?
All LDS3985PU15R products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LDS3985PU15R meets industry standards.
7.What is the process for return or replacement of LDS3985PU15R?
All LDS3985PU15R units undergo pre-shipment inspection (PSI). If there is an issue with LDS3985PU15R, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LDS3985PU15R part is unused and in its original packaging.
Return procedure for LDS3985PU15R:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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